1. Place the olive oil in a large saucepan over medium heat. Add the onion and celery, and saute, adding small amounts of chicken broth if necessary to prevent burning, until softened, about 5 minutes. Then add the chicken broth, water and carrots, and bring to a boil. Cook for 5 more minutes.

3. Dissolve the cornstarch in the half-and-half, then slowly stir into the hot soup. Stirring constantly, thicken the soup by bringing it to a boil. Serve with a sprinkle of cheddar cheese if using (adds 15 calories).